Ragactis lucida

Natural history. — Ragactis lucida lives in shallow waters attached to hard substratum, inside crevices or holes of coral rocks with only tentacles visible, in the fore and back-reef zones, at 4 – 6 m depth. It is associated to the shrimp Alpheus roquensis Knowlton & Keller, 1985 (Knowlton & Keller 1985) and Ancylomenes pedersoni is usually swimming above its tentacles, as is usually seen in Bartholomea annulata.

(Figure 11, Table 2)

Diagnosis. — Fully expanded tentacles and oral disc to 200 mm in diameter. Oral disc 12 – 28 mm in diameter, smooth, brownish, semi-transparent, lighter than tentacles, with small yellow spots around mouth (Figure 11 B). Tentacles 48 – 96, long, to 100 mm in length, slender, inner ones longer than outer ones, brown, semi-transparent; tentacles with numerous white spherical protuberances irregularly scattered (Figure 11 A – D). Column elongated, 25 – 36 mm in diameter and 42 – 55 mm in height, smooth, divided into capitulum and scapus (Figure 11 D). Capitulum brown or light brown with white dots (Figure 11 D). Pedal disc well developed, 15 – 22 mm in diameter, limbus with irregular contour (Figure 11 C). Pedal disc and scapus beige. One or two rows of cinclides in midcolumn. Mesenteries hexamerously arranged in four cycles (48 – 50 pairs in specimens examined): only first cycle perfect. No gametogenic tissue observed in specimens reviewed. Two pairs of directives each attached to a well developed siphonoglyph (Figure 11 E). Retractor muscles strong, diffuse to restricted; parietobasilar muscles poorly developed. Basilar muscles poorly developed. Marginal sphincter muscle not observed. Longitudinal muscles in distal column (Figure 11 F). Longitudinal muscles of tentacles ectodermal. Acontia white, with basitrichs and microbasic p - amastigophores. Zooxanthellae present (Figure 11 F). Cnidom: basitrichs, holotrichs, microbasic p - amastigophores and spirocysts (Figure 11 G – Q; see Table 2).

Remarks. — Ragactis lucida has a complicated taxonomic history, having been placed in several genera (Ocaña et al. 2007). It was originally described in Capnea Forbes, 1841. but subsequently transferred to Heteractis Milne- Edwards & Haime, 1851 (Duchassaing & Michelotti 1860, 1864). Later, Andres (1883) erected the genus Ragactis for R. pulchra and included R. lucida in this new group; however, Schmidt (1972) moved R. pulchra to Phymanthus — now Phymanthus pulcher (Andres, 1883) — and hence Ragactis lacks a type species (Fautin et al. 2007). Ragactis lucida has been also placed within Aiptasia (e. g. Duerden 1898; Pax 1910) and Bartholomea (e. g. Watzl 1922; Corrêa 1964). Although Carlgren’s (1949) diagnosis of Heteractis was based on R. lucida (as Heteractis lucida), and Heteractis had been used extensively for this species (e. g. McMurrich 1896; Stephenson 1920; Carlgren 1945, 1949; den Hartog 1977; Manjarrés 1978; Knowlton & Keller 1985; Varela et al. 2001; Ocaña et al. 2007), Dunn (1981) redefined Heteractis for species of the endomyarian family Stichodactilydae. Dunn (1981) suggested that H. lucida should be placed within Bartholomea (family Aiptasiidae) or otherwise within Capnea; however, Capnea currently includes species with endodermal marginal sphincter and without acontia or cinclides (Dunn 1983). According to Fautin (2011), the familial placement of Ragactis is uncertain; however the diagnostic characters of R. lucida fit with those of the family Aiptasiidae: weak or no mesogleal marginal sphincter, ectodermal longitudinal muscles in the distal column, cinclides, and acontia with basitrichs and microbasic p - amastigophores (Rodríguez et al. 2012). As previously suggested (Duerden 1898, 1902 b; Dunn 1981), we find remarkable similarities in external and internal morphology between R. lucida and B. annulata: apparently they only differ in the tentacular structures. Nonetheless, further revision is necessary to address this synonymy. According to Fautin (2011), Ragactis has two valid species; however, differences between species remain unclear due to scarce information about R. hyalina (Le Sueur, 1817).

Distribution. — From Bahamas to Barbados, along the entire Caribbean Sea (see Table 1). In the Mexican Caribbean, this species is reported for Puerto Morelos reef (INE 2000), but this is the first record for Majahual reef.

Material examined. — Majahual (18 ° 42 ’ 28.18 ” N, 87 ° 42 ’ 36.92 ” W; 2 specimens).